Document 0311
 DOCN  M9550311
 TI    Backcalculation models of age-specific HIV incidence rates.
 DT    9505
 AU    Rosenberg PS; National Cancer Institute, Epidemiologic Methods Section,;
       Rockville, Maryland 20892.
 SO    Stat Med. 1994 Oct 15-30;13(19-20):1975-90. Unique Identifier : AIDSLINE
       MED/95148996
 AB    This paper extends the use of backcalculation to estimate past incidence
       of HIV infection in different age groups from age-specific counts of
       AIDS incidence. The approach is flexible and allows the distribution of
       age at HIV infection to change over time. In this new approach, the
       incubation distributions used to backcalculate HIV infection rates
       depend on the age at HIV infection, because younger age is associated
       with slower progression. The effect of age on progression is estimated
       from a joint analysis of natural history data from several cohort
       studies of gay and bisexual men. As in previous applications, the
       incubation distributions also change over time to accommodate treatment
       effects and the 1987 revision of the surveillance definition. The method
       is applied to AIDS incidence data for the United States population.
       Estimated infection incidence for the entire population declined from
       peak levels seen in the mid-1980s. However, persons under age 25 years
       have accounted for an increasing proportion of new HIV infections as the
       epidemic has progressed. Quantitative estimates were sensitive to the
       assumed incubation distribution, but the trend toward younger age at HIV
       infection was apparent using several models of the incubation
       distribution. Although the models are computationally intensive, they
       provide useful information about seroincidence trends in different age
       groups.
 DE    Acquired Immunodeficiency Syndrome/*EPIDEMIOLOGY  Adult  Age of Onset
       Age Factors  Cohort Studies  Disease Progression  Homosexuality, Male
       Human  HIV Infections/*EPIDEMIOLOGY  HIV Seropositivity/*EPIDEMIOLOGY
       Incidence  Likelihood Functions  Male  Middle Age  *Models, Biological
       Time Factors  JOURNAL ARTICLE

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